Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751373AbaGCFKu (ORCPT ); Thu, 3 Jul 2014 01:10:50 -0400 Received: from mga14.intel.com ([192.55.52.115]:14919 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750867AbaGCFKs (ORCPT ); Thu, 3 Jul 2014 01:10:48 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.01,592,1400050800"; d="scan'208";a="556766661" Date: Thu, 3 Jul 2014 13:11:42 +0800 From: Wanpeng Li To: Bandan Das Cc: Paolo Bonzini , Jan Kiszka , Gleb Natapov , Hu Robert , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] KVM: nVMX: Fix IRQs inject to L2 which belong to L1 since race Message-ID: <20140703051142.GA2687@kernel> Reply-To: Wanpeng Li References: <1404284054-51863-1-git-send-email-wanpeng.li@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Bandan, On Wed, Jul 02, 2014 at 12:27:59PM -0400, Bandan Das wrote: >Wanpeng Li writes: > >> This patch fix bug https://bugzilla.kernel.org/show_bug.cgi?id=72381 >I can also reproduce this easily with Linux as L1 by "slowing it down" >eg. running with ept = 0 > >I suggest changing the subject to - >KVM: nVMX: Fix race that incorrectly injects L1's irq to L2 > Ok, I will fold this to next version. ;-) >> If we didn't inject a still-pending event to L1 since nested_run_pending, >> KVM_REQ_EVENT should be requested after the vmexit in order to inject the >> event to L1. However, current log blindly request a KVM_REQ_EVENT even if > >What's current "log" ? Do you mean current "code" ? > Yeah, it's a typo. I mean "logic". [...] >Also, I am wondering isn't it enough to just do this to avoid this race ? > > static int vmx_interrupt_allowed(struct kvm_vcpu *vcpu) > { >- return (!to_vmx(vcpu)->nested.nested_run_pending && >+ return (!is_guest_mode(vcpu) && >+ !to_vmx(vcpu)->nested.nested_run_pending && > vmcs_readl(GUEST_RFLAGS) & X86_EFLAGS_IF) && > !(vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) & > I don't think you fix the root cause of the race, and there are two cases which I concern about your proposal: - If there is a special L1 which don't ask to exit on external intrs, you will lose the intrs which L0 inject to L2. - If inject_pending_event fail to inject an intr since the change that you made in vmx_interrupt_allowed, L0 will request an intr window for L2, however, the intr is belong to L1. Regards, Wanpeng Li >Thanks, >Bandan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/